The invention relates to a mixing valve for mixing water from hot and cold water sources to control the temperature of the mixed-water output and, more particularly, to a mixing valve having a limit stop that limits the proportion of hot water to control the maximum temperature of the mixed-water output.
Mixing valves are well known and commonly used in showers to permit the user to mix water from the hot and cold-water sources to produce a combined or resultant water output at a temperature desired by the user. Mixing valves are available in many different forms. For example, such valves can include combined or separate on-off valves along with hot and cold mixing valves. Mixing valves can also be constructed for proportionally increasing both the cold-water supply and the hot-water supply to obtain the desired temperature or for maintaining the cold-water supply at a fixed supply rate and then increasing the proportion of the hot water to obtain the desired temperature.
Many shower valves are now thermostatically controlled. Such a valve contains a thermostatic element responsive to temperature change that operates to actuate a plunger or similar device to restrict the hot water when the mixed output exceeds a predetermined temperature. The thermostat can be adjusted to select the maximum temperature of the output.
Regardless of the type of mixing valve, all mixing valves have a maximum proportional contribution from the hot-water supply, which defines the maximum temperature of the output. The maximum temperature obtainable from the mixing valve is a function of the hot- and cold-water flow rates and the temperature differential between the hot and cold water. At the maximum hot-water flow rate, it is not uncommon for the resultant output flow to exceed a temperature that is comfortable for the user. Therefore, it is desirable to provide a stop that prevents the setting of the valve at a temperature greater than that comfortable to the user. Also, it is desirable to provide pre-sets that position the valve at a location in which the resultant mixed outflow will have a desired and user-specified temperature.